1. Field of the Invention
The present invention relates to an electronic watch, and more specifically it relates to an electronic watch having an internal electrical generating mechanism, and in particular an electronic watch which also has a chronograph function.
2. Description of the Related Art
In the past multifunction electronic watches having not only a time function, but also a such functions as a chronograph function and alarm function have been developed and manufactured. These multifunction electronic watches differ, depending upon watch functions are added to the time function, and for this reason an internal microcomputer has been used, enabling a change in the specifications for various different products.
In a multifunction watch such as this, because it is necessary to have a single hand indicate a variety of elements, for example, the current time and the alarm time, a hand position counter is caused to coincide with, for example, a current time counter, so as to achieve an indication by means of the hand.
For this reason, it was necessary to first perform the operation of causing the hand position to coincide with the hand position counter, this being known as the reference position adjustment operation.
This reference position adjustment operation needed to be performed each time the internal circuit took on an indeterminate state because of, for example, battery replacement, and was extremely troublesome.
As a method of solving this problem, an electronic watch was disclosed by the applicant in Japanese Patent Application No. 5-517803, in which, when a decrease in the battery voltage is detected, the contents of a hand position counter are saved in a non-volatile memory, these contents being transformed to the hand position counter after battery replacement, thereby eliminating the need for hand setting.
In the past an electronic watch has been developed and manufactured which has an electrical generating mechanism such as a solar cell and an electric power storage means such as an electric two layered condenser or a secondary cell, thereby eliminating the need for battery replacement. These watches, not requiring battery replacement, were extremely convenient.
A supply in the form of the above-noted electrical power generation means such formed by an electrical generating means and electric power storage means exhibit a wide variation in voltage, and can sometimes exhibit a change in voltage similar to that encountered when a conventional battery is replaced.
Namely, the voltage thereof can be varied by crossing an operational limit voltage of the electric watch.
For this reason, when applying this power supply to a multifunction watch, the above-noted technique for hand position storage is extremely effective. If this technique is not provided, each time the power supply voltage falls below the operational limit voltage, it is necessary to perform a reference position adjustment.
However, even when the above-noted hand position storage technique is applied, if the power supply voltage varies in the region surrounding the operational limit voltage, it is necessary to repeatedly perform the hand position writing and hand position reading operations, thereby resulting not only in wasteful consumption of electrical power, but also in the possibility that the writing and reading operations will not be performed accurately.
In addition, in the above-noted electronic watch having an electrical generation mechanism, if the amount of charge of the electrical power storage means which is the electrical generation means as a power supply means, is insufficient, it was necessary to notify the user of this condition, as a prompt to perform charging.
As a means of solving this problem, in accordance with the disclosure in the Japanese Unexamined Patent Publication (KOKAI) No. 62-194484, by changing the type of movement of the second hand, notification is made of the insufficient charge, and if the voltage is restored after the watch has stopped, hand movement different that the above is performed, to notify the user that the watch had stopped, and that the displayed time has been disturbed.
However, in the above-noted technology, because the second hand continues to be driven even when the voltage of the electrical power storage means has decreased, valuable electrical power is consumed, this resulting in an acceleration of the drop in the voltage of the secondary cell.
However, if the second hand is stopped, there is a danger that the user might be caused to misinterpret this as indicating that the watch has totally stopped, if the second hand is merely stopped, the value of the watch as a product will decrease.